The present invention relates to a suspension device for the load-bearing and resilient support of a wheel of a motor vehicle. The device comprises at least one spring cylinder with a piston, which is guided in a manner moveable relative to it in a pressure cylinder, and comprising a driving device for converting pivoting movements of a wheel oscillating-crank supporting arm, which movements oscillate about an oscillating-crank axis parallel to a wheel axis, into relative movement between the pressure cylinder and piston. The piston acts counter to an elastic compressible spring medium in order to produce a load-bearing supporting spring force.
Suspension devices of the general type of this invention are used primarily in heavier wheeled and caterpillar-type motor vehicles. In this case, each load-bearing vehicle wheel has a dedicated suspension which is independent of the other wheels, having a dedicated suspension device having a spring cylinder which, by interaction with a hydropneumatic spring energy store, produces the supporting spring force for the particular wheel. The wheel is mounted at a free end of a wheel oscillating-crank supporting arm. A shaft is connected to the supporting arm acting counter to the spring cylinder or to the piston thereof via a driving device.
In the case of a known suspension device of the type described previously, the driving device is designed in the manner of a connecting-rod drive, an eccentric lever, which, for its part, is connected in an articulated manner to a connecting rod coupled to the piston of the spring cylinder being connected to the shaft. A connecting-rod drive of this type has the disadvantage here of the transmission of force not being linear, but rather changing in accordance with a sine function because of the pivoting movement of the eccentric lever. Unfavorable lever ratios therefore arise in such a manner that, on the one hand, the supporting force can be achieved only by means of a relatively great pressure, and, on the other hand, it is possible to achieve only a relatively small spring travel (spring stroke) which is often insufficient especially for off-road vehicles. Furthermore, in the case of known suspension devices, a damping device for damping the suspension movements is provided by a hydraulic medium, which acts counter to the compressible (pneumatic) medium in order to produce the supporting spring force, flowing through a damping valve but, as a result, disadvantageously being rapidly heated because of the throttle action. This heating also has an effect on the compressible (pneumatic) medium by the pressure thereof, and therefore also the supporting spring force increasing. For the reasons mentioned, the known suspension device suffers from unfavorable, inconstant suspension and damping properties.
Furthermore, suspension devices of other types are also known with the supporting arm being connected in a rotationally fixed manner to a mechanical torsion bar spring which produces the supporting spring force. Systems of this type require a very large amount of installation space, since for each wheel a separate torsion bar spring extends transversely across the entire vehicle to the opposite side and has to be fastened therein in a rotationally fixed manner. In addition, mechanical friction dampers are also provided in mechanical suspension devices of this type.
The present invention is based on the object of providing a suspension device of the generic type described above, which is distinguished by great performance and improved suspension properties and, in particular, improved damping properties while having a compact constructional form.